In the mechanical jack industry, and specifically where mechanical jacks are used with trailers, there is a continuing need for novel apparatus and methods to improve the reliability and ease of maintenance of jack assemblies. Mechanical jacks commonly are comprised of a number of components retained within a housing. In order for a service technician to service, modify, or repair a jack, the technician must often disassemble and subsequently reassemble the jack. The disassembly is especially required when the service, modification, or repair regards a component positioned near the bottom of the jack. Internal mechanisms of jacks are normally accessed by removing a cover on the top of the jack and removing multiple components to gain access to the desired component or location. Once the service, modification, or repair is completed, the removed components are reinstalled and the cover is placed back on the jack. Disassembly and reassembly of the jack can often be time consuming, tedious, and may lead to the damaging of jack components.
In many prior art jacks, the components just below the cover are a cross shaft supported on a pair of bushings, a bevel pinion gear coupled to the shaft, and a mating bevel gear engaged with the pinion gear. A pin securing the pinion gear to the cross shaft is commonly held in place by an interference fit between the pin and apertures in the pinion gear and cross shaft. Such an interference fit may make it extremely difficult to remove the pin from the pinion gear and shaft apertures when it is necessary to service the jack. In order to service a jack, a technician may be required to forceably remove the pin from the apertures. Such forceable removal is commonly accomplished by placing a punch in contact with the pin and applying repeated hammer strokes to the punch to dislodge the pin from the apertures. This processes of hammering often leads to permanent damage to the pin, the pinion gear, and the shaft. Repeated hammer strokes applied to the pin may also result in the pin being pushed down into the jack assembly, further damaging other components of the jack. In addition, the pin may be pushed down into a location within the jack assembly where it cannot be easily retrieved by the technician.
The cross shaft is commonly coupled to a jack by bushings positioned in the walls of a jack housing. Such bushings are commonly retained in the jack housing by an interference fit between the bushing and the bushing aperture in the wall of the housing. Similar to the interference fit of the pin described above, the interference fit of a bushing and an aperture in the housing may also result in difficulty in removing the bushing to service the jack. Hammering techniques may again be necessary to remove the bushing from the housing, leading to damage to the housing, the shaft, the bushing, and other components of the jack.
Additionally, the use of interference fits in the design of jack assemblies necessitates the manufacturing of pins, bushings, shafts, pinion gears, and housings with relatively small or tight manufacturing tolerances and dimensional variances. Such restrictive tolerances and variances lead to costly manufacturing and assembly processes for original as well as replacement components and assemblies. Such tight tolerances also restrict the use of original or replacement parts to specific jack assemblies. Original and replacement pins, bushings, shafts, pinion gears, and housings may fit only a small, select group of jacks, which may lead to costly levels of inventory and long lead times in obtaining replacement parts.
The disadvantages of the prior art as described herein, make it desirable to develop novel apparatus and methods regarding jack assemblies to facilitate more efficient and reliable servicing methods to reduce the time needed to service a jack assembly and reduce damage to jack components during servicing. Further, it is useful to eliminate the need for relatively tight manufacturing tolerances and variances. Accordingly, novel apparatus and methods for securing a pinion gear to a cross shaft or securing a bushing to a jack housing that overcome the disadvantages of the prior art are desired.